How to replace the CMOS battery

Updated: 06/30/2020 by Computer Hope

There are several reasons the CMOS battery needs to be replaced in your computer. This page provides information on why you would need a replacement, and the steps to fix it.

Why do I need to replace my CMOS battery?

  • Computer is losing its time or date settings.
  • An error or alert message, like the following, is displayed when the computer boots.
  • CMOS Read Error
  • CMOS Checksum Error
  • CMOS Battery Failure
  • System battery voltage is low

If any of the issues or messages above are encountered, you likely need to replace the CMOS battery. The process to replace it is detailed in the following sections.

Locate your CMOS battery

Caution

When inside your computer, make sure you are aware of ESD and its dangers.

CMOS battery

Open the computer case and find the battery on the motherboard. Verify it is accessible and can be removed. Today, most computers use a coin cell CMOS battery, like the CR2032 battery shown in the picture.

Tip

Some CMOS batteries may be held down by a metal clip or bar. The battery can be removed by sliding it out from under the clip. Do not bend this clip to get the battery out, as a bent clip can result in the new battery not staying in the socket.

If you cannot locate the CMOS battery, refer to the motherboard documentation or contact the computer manufacturer. If you no longer have the documentation for the motherboard, it's likely you can find it online.

Note

With some computers, you may need to disconnect cables, remove drives, or remove other parts of the computer to get full access to the CMOS battery.

Obtain battery information

Unfortunately, most manufacturers do not list the exact type and model of the CMOS battery. Once you have located the battery, we recommend you write down its specifications (voltage, chemistry, wiring). If possible, remove the battery and take it to a retail location.

Tip

For most computers, the model of the battery is CR2032.

Removing the battery

If your computer uses a coin cell battery, removing the battery is relatively simple. Use your fingers to grab the edge of the battery and pull it up and out of the socket holding it in place. Some motherboards have a clip holding the battery down. If your computer's motherboard has this clip, you may need to use one hand to move the clip up and the other hand to pull the battery out.

Caution

When inside your computer, make sure you are aware of ESD and all its potential dangers.

Unfortunately, not all CMOS batteries are removable. Some manufacturers only allow a replacement battery to be added. If your computer does not have a coin cell battery, refer to your documentation or contact your computer manufacturer for further assistance.

If your computer's motherboard does not have a removable battery, you need to set a jumper on the motherboard to install the new battery.

Insert the new battery

After purchasing a new battery, remove the old battery and replace it with the new battery. Some computers may not have a removable battery, for these computers insert the new battery into the secondary battery socket on the motherboard.

Enter CMOS values

Once the battery has been replaced, turn on the computer and reset the CMOS values to the defaults. After the values have all been entered, make sure to save the settings before exiting. Many CMOS setups allow you to press a key, such as F10, to save values and exit with one action.

Bad hardware

If you continue to receive the error after following all the steps above, this is a sign of a more serious issue. The most likely causes are a bad power supply or bad motherboard. You may need to look into replacing the power supply or the motherboard to resolve the issue. At this point, we would recommend taking your computer to a computer repair shop to have them diagnose the issue.

Additional information